Both isocratic and gradient chromatography systems are known in the prior art, each being utilized for specific applications and each utilizing the same basic components.
A complete, turnkey isocratic chromatographic system consists of the following components:
1. A chromatography column containing column packings or separation medium wherein the actual separation takes place.
2. A pump, syringe, sample injector or a sample loop to inject a sample onto the column.
3. A fluid delivery system, such as a metering pump, to feed starting, elution or wash buffer materials into the column.
4. A detector (which measures for example, absorption or emission in the ultraviolet, infrared, visible region, electrochemical potential, radioactivity, conductivity etc.,) to measure the concentration of the components in the separated stream coming out of the column.
5. A fraction collector which collects various fractions of components separated on the column and eluted at different rates. The fraction collector can be programmed to do the collection as a function of time, volume, number of drops per unit time or peak collection based on input from the detector.
6. Various other monitors, e.g., pressure and flow, to establish the status of the process at any given time.
7. Data acquisition equipment which records the chromatograms of the eluting compounds and can calculate the composition of the various components.
8. A process controller, which may be in the form of a computer or microprocessor, to interface with each of the above-described components.
9. Assorted piping and valving.
A gradient chromatography system uses the same general components as the isocratic system, the primary difference being in the solvent delivery which has to deliver a mixture of fluids whose composition varies continuously as a function of time. The gradient technique is often used to separate peaks that may elute close together in an isocratic mode and need small changes in elution conditions to achieve differential separation. This is accomplished by using two pumps, each of which is connected to a particular buffer chamber, and independently pump the fluid streams into a mixer where both the buffers are mixed and the mixture is them delivered to the column. The pumping rates are controlled by a gradient programmer which is designed to vary the flow rates to achieve the desired combination of flow rate and composition.
In many instances where the limit buffer is responsible for creating a specific gradient (e.g., ionic or pH) an additional detector, such as a pH meter or conductivity meter, may be used downstream of the column to monitor the gradient profile.
In the last decade, many advancements have been made, as integrated chromatographic systems have become more sophisticated and responsive. For example, the need for faster separations with higher resolution have given rise to rigid, small size column packings as opposed to larger size soft gels. The newer, high performance liquid chromatography (HPLC) systems, however, operate at very high pressures, such as 1000-4000 psi, which requires special pumps, high pressure tubing and valving, and special column and accessory designs. The cost of these systems, consequently, is very high.
As the need for higher performance has started to extend beyond the analytical laboratory to production chromatography systems, the problem has taken on a new dimension. The cost of preparative systems has escalated tremendously. Furthermore, such systems operating at these high pressures are being used in routine production environment, which can be a serious hazard. The industry is thus in the position of having to choose between low pressure, low cost systems which are slow and have limited purification capabilities, or high pressure, high performance systems which are significantly more expensive and pose a health hazard. Thus, a need exists in the art of chromatography for a system which is capable of high performance without resorting to high pressure and the associated hazards and high costs.
Therefore, it is an object of this invention to provide a chromatography system capable of high performance while operating at relatively low pressures.
Another object of this invention is to provide a chromatography system, either isocratic, gradient or ternary, which utilizes horizontal flow through the separation medium in the columns, while providing low pressure, high performance operation.
A further object of this invention is to provide a chromatography system using horizontal (radial) flow columns capable of use in analytical, pilot or production applications.
Another object of the invention is to provide a chromatography system capable of use in both isocratic and gradient applications and which produces rapid separations with either conventional gels or with high performance packings, without high operating pressures and high equipment cost.
Additional objects, advantages and novel features of the invention, together with additional features contributing thereto and advantages accruing therefrom will be apparent to those skilled in the art, from the following description of the invention which is shown in the accompanying drawings which are incorporated herein by reference and form an integral part hereof. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.